Can you build a business on open source?

Yes. Open-source products offer an ideal opportunity. One of the basic myths 
 about open source comes in variations such as “Programmers can’t eat code. They need money…”
 or “Even a chicken won’t scratch for nothing…” It’s true that plenty of open-source projects won’t earn you 
 enough to buy a meal. There’s also a wide range of open-source projects that can be
 a gold mine for business.

What got me thinking about this, in the best sense, was the post JBoss on the rise 
 by Pavel Kolesnikov. JBoss is one of the projects that shows how successfully you can build a business 
 on open source. Let me quote the end of Pavel’s post.

True, nobody in the Czech Republic is actively working as a JBoss partner yet, but that could change soon.

Absolutely true. Why hasn’t anyone taken advantage of what JBoss offers yet?
 I genuinely don’t understand it. From what I can see, JBoss is very popular 
 with developers. And professional services such as training, consulting and other support are something
 some of them would surely pay for.

The same goes for projects such as Eclipse, Hibernate and Spring. You just need to find the right way to use them in your business. I don’t have to look far for an example. 
 I’m working on a commercial project built on Eclipse right now. Whether you end up with 
 a solution built on open source or services around an open-source product,
 the business potential is enormous.